CCR1 and, to a lesser extent, CCR5, the receptors for CCL3 and CCL4, were found in CLL-derived monocyte-macrophages. Consistently, CCL3 increased monocyte migration, and CD68 + macrophage infiltration was particularly high in BMB from CD38 + CD49d + CLL. Conditioned media from CCL3-stimulated macrophages induced endothelial cells to express vascular cell adhesion molecule-1 (VCAM-1), the CD49d ligand, likely through tumor necrosis factor A overproduction. These effects were apparent in BMB from CD38 + CD49d + CLL, where lymphoid infiltrates were characterized by a prominent meshwork of VCAM-1 + stromal/endothelial cells. Lastly, CD49d engagement by VCAM-1 transfectants increased viability of CD38 + CD49d + CLL cells. Altogether, CD38 and CD49d can be thought of as parts of a consecutive chain of events ultimately leading to improved survival of CLL cells. [Cancer Res 2009;69(9):4001-9]

IGHV3-21-using chronic lymphocytic leukemia (CLL) is a distinct entity

In chronic lymphocytic leukemia (CLL), NOTCH1 mutations have been associated with clinical resistance to the anti-CD20 rituximab, although the mechanisms behind this peculiar behavior remain to be clarified. In a wide CLL series (n=692), we demonstrated that CLL cells from NOTCH1-mutated cases (87/692) were characterized by lower CD20 expression and lower relative lysis induced by anti-CD20 exposure in vitro. Consistently, CD20 expression by CLL cells was upregulated in vitro by γ-secretase inhibitors or NOTCH1-specific small interfering RNA and the stable transfection of a mutated (c.7541-7542delCT) NOTCH1 intracellular domain (NICD-mut) into CLL-like cells resulted in a strong downregulation of both CD20 protein and transcript. By using these NICD-mut transfectants, we investigated protein interactions of RBPJ, a transcription factor acting either as activator or repressor of NOTCH1 pathway when respectively bound to NICD or histone deacetylases (HDACs). Compared with controls, NICD-mut transfectants had RBPJ preferentially complexed to NICD and showed higher levels of HDACs interacting with the promoter of the CD20 gene. Finally, treatment with the HDAC inhibitor valproic acid upregulated CD20 in both NICD-mut transfectants and primary CLL cells. In conclusion, NOTCH1 mutations are associated with low CD20 levels in CLL and are responsible for a dysregulation of HDAC-mediated epigenetic repression of CD20 expression.

CD49d and CD38 are independent negative prognostic markers in chronic lymphocytic leukemia (CLL). Their associated expression marks a disease subset with a highly aggressive clinical course. Here, we demonstrate a constitutive physical association between the CD49d/CD29 integrin complex and CD38 in primary CLL cells and B-cell lines by (i) cocapping, (ii) coimmunoprecipitation and (iii) cell adhesion experiments using CD49d-specific substrates (vascular-cell adhesion molecule-1 or CS-1/H89 fibronectin fragments). The role of CD38 in CD49d-mediated cell adhesion was studied in CD49d þ CD38 À cells (P ¼ 0.0006) and a more complex distribution of F-actin to the adhesion sites. Lastly, adherent CD49d þ CD38 þ cells were more resistant to serum-deprivation-induced (Po0.001) and spontaneous (P ¼ 0.03) apoptosis than the CD49d þ CD38 À counterpart. Altogether, our results point to a direct role for CD38 in enhancing CD49d-mediated adhesion processes in CLL, thus providing an explanation for the negative clinical impact exerted by these molecules when coexpressed in neoplastic cells.